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Predictive values of methicillin-resistant Staphylococcus aureus nasal swabs for pneumonia in burn ICU patients
Zachary Carlson1, Robyn Stoianovici1, Sierra Young1
1Department of Clinical Pharmacy, UC Davis Medical Center, Sacramento, CA, USA.
Introduction/Objective:
This retrospective cohort study aimed to determine the sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) of MRSA nasal swabs for pneumonia in burn-injured intensive care unit (ICU) patients.
Methods:
Patients 18 years or older admitted to the Burn ICU at a tertiary medical center from 2016 to 2021 were included if they had any burns, a pneumonia ICD-10 code, an MRSA nasal swab obtained during admission, and any respiratory cultures associated with at least five consecutive days of antibiotics.
Results:
There were 267 occurrences of pneumonia across 136 patients. MRSA nasal swabs had an overall sensitivity of 39 %, specificity of 98.7 %, PPV of 84.2 %, and NPV of 89.9 %. MRSA nasal swabs obtained less than seven days from antibiotic initiation had a specificity of 98.6 % and NPV of 98.6 %; meanwhile, swabs obtained at least seven days from antibiotic initiation had a specificity of 98.7 % and NPV of 86.4 %.
Conclusions:
The high specificity and NPV indicate that negative MRSA nasal swabs obtained less than seven days from antibiotic initiation may be used to de-escalate anti-MRSA antibiotics in clinically stable burn-injured patients with suspicion of pneumonia. The decrease in NPV suggests that it may be beneficial to obtain a repeat swab periodically.
Insights
Negative MRSA nasal swabs in burn ICU patients with suspected pneumonia are highly specific and accurate for ruling out infection. This can help de-escalate antibiotics, but repeat swabs may be beneficial.
Area of Science:
- Infectious Disease
- Critical Care Medicine
- Burn Surgery
Background:
- Pneumonia is a common complication in burn-injured intensive care unit (ICU) patients.
- Accurate early diagnosis is crucial for appropriate antibiotic selection and de-escalation.
Purpose of the Study:
- To evaluate the diagnostic performance of Methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs for pneumonia in burn ICU patients.
- To determine the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MRSA nasal swabs.
Main Methods:
- Retrospective cohort study of adult burn ICU patients (2016-2021).
- Inclusion criteria: burns, pneumonia diagnosis, MRSA nasal swab on admission, and respiratory cultures with >=5 days of antibiotics.
- Analysis of swab timing relative to antibiotic initiation.
Main Results:
- 267 pneumonia cases in 136 patients.
- Overall MRSA nasal swab sensitivity: 39%, specificity: 98.7%, PPV: 84.2%, NPV: 89.9%.
- Swabs <7 days from antibiotics: specificity 98.6%, NPV 98.6%. Swabs >=7 days: specificity 98.7%, NPV 86.4%.
Conclusions:
- High specificity and NPV of MRSA nasal swabs suggest utility in de-escalating anti-MRSA antibiotics in stable burn patients with suspected pneumonia, especially when obtained <7 days from antibiotic initiation.
- The declining NPV with later sampling indicates potential benefit from periodic repeat swabs.
- Negative MRSA nasal swabs can guide antibiotic stewardship in this vulnerable patient population.
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